KS0085 Keyestudio Smart Home Kit for Arduino

Instruction:

This Smart Home Learning Kit based on the Arduino platform is newly rolled out by Keyestudio DIY Robot Co. Ltd. It simulates the real smart home and demonstrates the cozy and comfortable life for people.
This system adopts PLUS main control board and multiple modules, including 1602 LCD, photocell sensor, analog gas(MQ-2) sensor, PIR motion sensor, yellow LED, servo, steam sensor and Bluetooth.
In fact, Bluetooth controls everything in smart home: light intensity, humidity, flammable gas concentration, doors openning and closing. Everything is controlled via APPs on smart phones/IPad and will be displayed on 1602 LCD in real time.
We totally provide 3 programming languages: C language, Mixly and Scratch. These languages hit the top list in programming, which is easy and convenient to use and understand.

Kit List

Download software and install driver

Download software

When we get control board, we need to download Arduino IDE and driver firstly. You could download Arduino IDE from the official website: https://www.arduino.cc/, click the SOFTWARE on the browse bar, click “DOWNLOADS” to enter download page, as shown below:

There are various versions for Arduino, just download a suitable version for your system, we will take WINDOWS system as an example to show you how to download and install.

There are two versions for WINDOWS system, one is installed version, another one is download version, you just need to download file to computer directly and unzip it. These two versions can be used normally. Choose one and download on your computer.

You just need to click JUST DOWNLOAD, then click the downloaded file to install it. And when the ZIP file is downloaded, you can directly unzip and start it.

Keyestudio PLUS Control Board

Description

Keyestudio PLUS control board is fully compatible with Arduino IDE development environment. It contains all the functions of the Arduino UNO board. Moreover, some improvements we made highly strengthen its function. It is the best choice to learn how to build circuit and write code as well. Let’s get started!

Serial communication interface: D0 is RX, D1 is TX
PWM interface (pulse width modulation): D3 D5 D6 D9 D10 D11
External interrupt interface: D2 (interrupt 0) and D3 (interrupt 1)
SPI communication interface: D10 is SS, D11 is MOSI, D12 is MISO, D13 is SCK
IIC communication port: A4 is SDA, A5 is SCL

Installing driver

Let’s install the driver of keyestudio PLUS control board. The USB-TTL chip on PLUS board adopts CP2102 serial chip. The driver program of this chip is included in Arduino 1.8 version and above, which is convenient. Plug on USB port of board, the computer can recognize the hardware and automatically install the driver of CP2102.

If install unsuccessfully, or you intend to install manually, open the device manager of computer. Right click Computer----- Properties----- Device Manager.

There is a yellow exclamation mark on the page, which implies installing the driver of CP2102 unsuccessfully. Then we double click the hardware and update the driver.

Click “OK” to enter the following page, click “browse my computer for updated driver software”, find out the installed or downloaded ARDUINO software. As shown below:

There is a DRIVERS folder in Arduino software installed package（）, open driver folder and you can see the driver of CP210X series chips.

We click “Browse”, then find out the driver folder, or you could enter “driver” to search in rectangular box, then click “next”, the driver will be installed successfully. (I place Arduino software folder on the desktop, you could follow my way)

Open device manager, we will find the yellow exclamation mark disappear. The driver of CP2102 is installed successfully.

Arduino IDE Setting

Click icon，open Arduino IDE.

To avoid the errors when uploading the program to the board, you need to select the correct Arduino board that matches the board connected to your computer. Then come back to the Arduino software, you should click Tools→Board, select the board. (as shown below)

Then select the correct COM port (you can see the corresponding COM port after the driver is successfully installed)

Before uploading the program to the board, let’s demonstrate the function of each symbol in the Arduino IDE toolbar.

A- Used to verify whether there is any compiling mistakes or not.
B- Used to upload the sketch to your Arduino board.
C- Used to create shortcut window of a new sketch.
D- Used to directly open an example sketch.
E- Used to save the sketch.
F- Used to send the serial data received from board to the serial monitor.

Start your first program

Open the file to select Example, choose BLINK from BASIC, as shown below:

Set board and COM port, the corresponding board and COM port are shown on the lower right of IDE.

Click to start compiling the program, check errors.

Click to upload the program, upload successfully.

Upload the program successfully, the onboard LED lights on for 1s, lights off for 1s. Congratulation, you finish the first program.

How to Add a Library?

What are Libraries ? Libraries are a collection of code that makes it easy for you to connect to a sensor,display, module, etc. For example, the built-in LiquidCrystal library helps talk to LCD displays. There are hundreds of additional libraries available on the Internet for download. The built-in libraries and some of these additional libraries are listed in the reference.

Here we will introduce the most simple way for you to add libraries.

Step 1：After downloading well the Arduino IDE, you can right-click the icon of Arduino IDE.

Find the option "Open file location" shown as below:

Step 2: Enter it to find out libraries folder which is the library file of Arduino.

Step 3：Next to find out the“libraries”of smart home(seen in the link: https://fs.keyestudio.com/KS0085), as shown below:

You just need to replicate and paste into the libraries folder of Arduino IDE.

The library of home smart is successfully installed, as shown below:

Projects

Alright, let’s get straight to our projects. In this kit, there are 14 sensors and modules included. We will start with the simple sensor to make you know the smart home deeply. However, if you are an enthusiast with Arduino knowledge. You could skip theses steps, assemble the smart home kit directly(there is assembly video in the folder)

Note: In this course, the interface of each sensor / module marked with (G,-, GND) indicates the negative pole, G is connected to G or - or GND of sensor shield or control board; “V” implies positive pole which is linked with V or VCC or 5V.

Project 1: LED Blink

Description：

In previous lesson, we installed the driver of keystudio V4.0 development board, we start from simple projects. For this lesson we will perform “Arduion blinks LED”, which is the basic practice for starter. We provide a test code to control LED to perform blinking effect. In the code, you could set distinct flashing scene by changing the time of lighting on and off. Power on GND and VCC, the LED will light on when signal end S is high level, on the contrary, LED will turn off when signal end S is low level.

Specifications：

Control interface: digital port
Working voltage: DC 3.3-5V
Pin pitch: 2.54mm
LED display color: white
Size: 30 * 20mm
Weight: 3g

Equipment:

Sensor shield

We usually combine Arduino control board with other sensors, modules and multiple sensors, which is difficult to wire. Conversely, this sensor shield cover this problem, you just need to stack on keyestudio PLUS control board when you use it.

This shield can be directly inserted into 3PIN sensors, it breaks out the common used communication ports as well, such as serial communication, IIC communication, SPI communication. What’s more, the shield comes with a reset button and 2 signal lights.

Pins Description

Connection Diagram：

Next to wire, link LED module with D13 of shield.

Note: G, V and S of white LED module are linked with G, V and 13 of expansion board.

Test Code：

/*
Keyestudio smart home Kit for Arduino
Project 1
Blink
http://www.keyestudio.com
*/
void setup() {
  // initialize digital pin 13 as an output.
  pinMode(13, OUTPUT);
}
// the loop function runs over and over again forever
void loop() {
  digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);              // wait for a second
  digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);              // wait for a second
}//

Test Result：

Upload test code successfully, white LED starts blinking, lights on for 1000ms, lights off for 1000ms, alternately.

Code Explanation

The code looks long and clutter, but most of which are comment. The grammar of Arduino is based on C.
Comments generally have two forms of expression:

/* .......*/ : suitable for long paragraph comments

// : suitable for mono line comments

So the code contains the many vital information, such as the author, the issued agreement, etc.

Most people omit comments, starter should develop a good habit of looking through code. Firstly, check comments. They contain the provided information and do help you understand test code quickly. Secondly, form the habit of writing comments

// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin 13 as an output.
  pinMode(13, OUTPUT);
}

According to comments, we will find that author define the D13 pin mode as digital output in setup() function. Setup() is the basic function of Arduino. It will execute once in the running of program, usually as definition pin, define and ensure the variables.

// the loop function runs over and over again forever
void loop() {
  digitalWrite(13, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);              // wait for a second
  digitalWrite(13, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);              // wait for a second
}

Loop() is the necessary function of Arduino, it can run and loop all the time after “setup()” executes once
In the loop()function, author uses
digitalWrite(13, HIGH); // turn the LED on (HIGH is the voltage level)

digitalWrite(): set the output voltage of pin to high or low level. We make D13 output high level, then the LED lights on.
delay(1000); // wait for a second
Delay function is used for delaying time, 1000ms is 1s, unit is ms

digitalWrite(13, LOW); // turn the LED off by making the voltage LOW
Similarly, we make D13 output low level, LED will turn off.
delay(1000); // wait for a second

Delay for 1s, light on LED--keep on 1s--light off LED--stay on 1s, iterate the process. LED flashes with 1-second interval. What if you want to make LED flash rapidly? You only need to modify the value of delay block. Reducing the delay value implies that the time you wait is shorter, that is, flashing rapidly. Conversely, you could make LED flash slowly.

Project 2: Breathing Light

Description

In the previous lesson, we control LED on and off and make it blink. In this project, we will control LED brightness through PWM to simulate breathing effect. Similarly, you can change the step length and delay time in the code so as to demonstrate different breathing effect.

PWM is a means of controlling the analog output via digital means. Digital control is used to generate square waves with different duty cycles (a signal that constantly switches between high and low levels) to control the analog output.In general, the input voltage of port are 0V and 5V. What if the 3V is required? Or what if switch among 1V, 3V and 3.5V? We can’t change resistor constantly. For this situation, we need to control by PWM.

For the Arduino digital port voltage output, there are only LOW and HIGH, which correspond to the voltage output of 0V and 5V. You can define LOW as 0 and HIGH as 1, and let the Arduino output five hundred 0 or 1 signals within 1 second. If output five hundred 1, that is 5V; if all of which is 1, that is 0V. If output 010101010101 in this way then the output port is 2.5V, which is like showing movie. The movie we watch are not completely continuous. It actually outputs 25 pictures per second. In this case, the human can’t tell it, neither does PWM. If want different voltage, need to control the ratio of 0 and 1. The more 0,1 signals output per unit time, the more accurately control.

Equipment：

Connection Diagram：

Note: on sensor shield, the G, V and S pins of yellow LED module are linked with G, V and 5.

Test Code：

 /*
Keyestudio smart home Kit for Arduino
Project 2
PWM
http://www.keyestudio.com
*/
int ledPin = 5; // Define the LED pin at D5
void setup () {
      pinMode (ledPin, OUTPUT); // initialize ledpin as an output.
}
void loop () {
for (int value = 0; value<255; value = value + 1) {
     analogWrite (ledPin, value); // LED lights gradually light up
     delay (5); // delay 5MS
   }
   for (int value = 255; value>0; value = value-1) {
     analogWrite (ledPin, value); // LED gradually goes out
     delay (5); // delay 5MS
   }}
//

Test Result：

Upload test code successfully, LED gradually becomes brighter then darker, like human breath, rather than light on and off immediately

Code analysis

When we need to repeat some statements, we have to use “for” statement For statement format as follows:

“for” cyclic sequence:

Round 1：1 → 2 → 3 → 4

Round 2：2 → 3 → 4
… Until number 2 is not established, “for”loop is over,
After knowing this order, go back to code:

for (int value = 0; value < 255; value=value+1){
        ...
}
for (int value = 255; value >0; value=value-1){
       ...
}

The two “for”statement make value increase from 0 to 255, then reduce from 255 to 0, then increase to 255,....infinite loop
There is a new function in “for” statement ----- analogWrite()

We know that digital port only has two state of 0 and 1. So how to send an analog value to a digital value? Here, we need this function, observe the Arduino board and you will find 6 pins with “~”. They are different from other pins and can output PWM signals.

Function format as follows:
analogWrite(pin,value) analogWrite() is used to write an analog value from 0~255 for PWM port, so the value is in the range of 0~255, attention that you only write the digital pins with PWM function, such as pin 3, 5, 6, 9, 10, 11.

PWM is a technology to obtain analog quantity through digital method. Digital control forms a square wave, and the square wave signal only has two states of switching (that is, high or low levels of our digital pins). By controlling the ratio of the duration of on and off, a voltage varying from 0 to 5V can be simulated. The time taken(academically referred to as high level) is called pulse width, so PWM is also called pulse width modulation.
Through the following five square waves, let’s know more about PWM.

In the above figure, the green line represents a period, and value of analogWrite() corresponds to a percentage which is called Duty Cycle as well. Duty cycle implies that high-level duration is divided by low-level duration in a cycle. From top to bottom, the duty cycle of first square wave is 0% and its corresponding value is 0. The LED brightness is lowest, that is, turn off. The more time high level lasts, the brighter the LED. Therefore, the last duty cycle is 100%, which correspond to 255, LED is brightest. 25% means darker.
PWM mostly is used for adjusting the LED brightness or rotation speed of motor.

Project 3: Passive Buzzer

Description

There are prolific interactive works completed by Arduino. The most common one is sound and light display. We always use LED to make experiments. For this lesson, we design circuit to emit sound. The universal sound components are buzzer and horns. Buzzer is easier to use. And buzzer includes about active buzzer and passive buzzer. In this experiment, we adopt passive buzzer. While using passive buzzer, we can control different sound by inputting square waves with distinct frequency. During the experiment, we control code to make buzzer sound, begin with “tick, tick” sound, then make passive buzzer emit “do re mi fa so la si do”, and play specific songs.

Equipment

Connection Diagram：

Note: The G, V, and S port of the passive buzzer module are separately connected to G, V, and 3 on the shield, power up.

Test Code：

 /*
Keyestudio smart home Kit for Arduino
Project 3.1
Buzzer
http://www.keyestudio.com
*/
int tonepin = 3; // Set the Pin of the buzzer to the digital D3
     void setup ()
     {
       pinMode (tonepin, OUTPUT); // Set the digital IO pin mode to output
     }
     void loop ()
     {
       unsigned char i, j;
       while (1)
       {
         for (i = 0; i <80; i ++) // output a frequency sound
         {
           digitalWrite (tonepin, HIGH); // Sound
           delay (1); // Delay 1ms
           digitalWrite (tonepin, LOW); // No sound
           delay (1); // Delay 1ms
         }
         for (i = 0; i <100; i ++) // output sound of another frequency
         {
           digitalWrite (tonepin, HIGH); // Sound
           delay (2); // delay 2ms
           digitalWrite (tonepin, LOW); // No sound
           delay (2); // delay 2ms
         }}}
//

Test Result：

From the above code, 80 and 100 decide frequency in “for” statement. Delay controls duration, like the beat in music.

We will play fabulous music if we control frequency and beats well, so let’s figure out the frequency of tones. As shown below:

After knowing the frequency of tone, next to control the time the note plays. The music will be produces when every note plays a certain amount of time. The note rhythm is divided into one beat, half beat, 1/4 beat, 1/8 beat, we stipulate the time for a note to be 1, half beat is 0.5, 1/4 beat is 0.25, 1/8 beat is 0.125....., Therefore, the music is played. We will take example of “Ode to joy”

From notation, the music is 4/4 beat.
There are special notes we need to explain:
1.Normal note, like the first note 3, correspond to 350(frequency), occupy 1 beat
2.The note with underline means 0.5 beat
3.The note with dot(3.)means that 0.5 beat is added, that is 1+0.5 beat
4.The note with”—” represents that 1 beat is added, that is 1+1 beat.
5.The two successive notes with arc imply legato, you could slightly modify the frequency of the note behind legato(need to debug it yourself), such like reducing or increasing some values, the sound will be more smoother.

/*
Keyestudio smart home Kit for Arduino
Project 3.2
Buzzer music
http://www.keyestudio.com
*/
#define NTD0 -1
#define NTD1 294
#define NTD2 330
#define NTD3 350
#define NTD4 393
#define NTD5 441
#define NTD6 495
#define NTD7 556
 
#define NTDL1 147
#define NTDL2 165
#define NTDL3 175
#define NTDL4 196
#define NTDL5 221
#define NTDL6 248
#define NTDL7 278
 
#define NTDH1 589
#define NTDH2 661
#define NTDH3 700
#define NTDH4 786
#define NTDH5 882
#define NTDH6 990
#define NTDH7 112
// List all D-tuned frequencies
#define WHOLE 1
#define HALF 0.5
#define QUARTER 0.25
#define EIGHTH 0.25
#define SIXTEENTH 0.625
// List all beats
int tune [] = // List each frequency according to the notation
{
  NTD3, NTD3, NTD4, NTD5,
  NTD5, NTD4, NTD3, NTD2,
  NTD1, NTD1, NTD2, NTD3,
  NTD3, NTD2, NTD2,
  NTD3, NTD3, NTD4, NTD5,
  NTD5, NTD4, NTD3, NTD2,
  NTD1, NTD1, NTD2, NTD3,
  NTD2, NTD1, NTD1,
  NTD2, NTD2, NTD3, NTD1,
  NTD2, NTD3, NTD4, NTD3, NTD1,
  NTD2, NTD3, NTD4, NTD3, NTD2,
  NTD1, NTD2, NTDL5, NTD0,
  NTD3, NTD3, NTD4, NTD5,
  NTD5, NTD4, NTD3, NTD4, NTD2,
  NTD1, NTD1, NTD2, NTD3,
  NTD2, NTD1, NTD1
};
float durt [] = // List the beats according to the notation
{
  1,1,1,1,
  1,1,1,1,
  1,1,1,1,
  1 + 0.5,0.5,1 + 1,
  1,1,1,1,
  1,1,1,1,
  1,1,1,1,
  1 + 0.5,0.5,1 + 1,
  1,1,1,1,
  1,0.5,0.5,1,1,
  1,0.5,0.5,1,1,
  1,1,1,1,
  1,1,1,1,
  1,1,1,0.5,0.5,
  1,1,1,1,
  1 + 0.5,0.5,1 + 1,
};
int length;
int tonepin = 3; // Use interface 3
void setup ()
{
  pinMode (tonepin, OUTPUT);
  length = sizeof (tune) / sizeof (tune [0]); // Calculate length
}
void loop ()
{
  for (int x = 0; x <length; x ++)
  {
    tone (tonepin, tune [x]);
    delay (350* durt [x]); // This is used to adjust the delay according to the beat, 350 can be adjusted by yourself.
    noTone (tonepin);
  }
  delay (2000); // delay 2S
}
//

Upload test code on the development board, do you hear “Ode to joy”?

Project 4：Controlling LED by Button Module

Description：

In this project, we will control LED to light on and off via button module. When the button is pressed, the signal end outputs low level (0); when released, the signal end of sensor keeps high level(1).

Equipment

Connection Diagram：

Note: The G, V, and S pins of button sensor module are separately connected to G, V, and 4 on the shield, and the G, V, and S pins of the yellow LED module are connected to G, V, and 5 on the shield.

Test Code：

Next to design the program, we make LED on by button. Comparing with previous experiments, we add a conditional judgement statement. We use if statement. The written sentences of Arduino is based on C language, therefore, the condition judgement statement of C is suitable for Arduino, like while, swich, etc.
For this lesson, we take simple “if” statement as example to demonstrate:

If button is pressed, digital 4 is low level, then we make digital 5 output high level , then LED will be on; conversely, if the button is released, digital 4 is high level, we make digital 5 output low level, then LED will go off.
As for your reference：


/ *
Keyestudio smart home Kit for Arduino
Project 4
Button
http://www.keyestudio.com
* /
int ledpin = 5; // Define the led light in D5
int inpin = 4; // Define the button in D4
int val; // Define variable val
void setup ()
{
pinMode (ledpin, OUTPUT); // The LED light interface is defined as output
pinMode (inpin, INPUT); // Define the button interface as input
}
void loop ()
{
val = digitalRead (inpin); // Read the digital 4 level value and assign it to val
if (val == LOW) // Whether the key is pressed, the light will be on when pressed
{digitalWrite (ledpin, HIGH);}
else
{digitalWrite (ledpin, LOW);}
}
//

Test Result：

This experiment is pretty simple, and widely applied to various of circuits and electrical appliances. In our life, you could find this principle on any device, such as the backlight is on when press any buttons, which is the typical appliance.

Project 5：1-channel Relay Module

Description

This module is an Arduino dedicated module, and compatible with arduino sensor expansion board. It has a control system (also called an input loop) and a controlled system (also called an output loop). Commonly used in automatic control circuits, the relay module is an "automatic switch" that controls a larger current and a lower voltage with a smaller current and a lower voltage.

Therefore, it plays the role of automatic adjustment, safety protection and conversion circuit in the circuit. It allows Arduino to drive loads below 3A, such as LED light strips, DC motors, miniature water pumps, solenoid valve pluggable interface. The main internal components of the relay module are electromagnet A, armature B, spring C, moving contact D, static contact (normally open contact) E, and static contact (normally closed contact) F, (as shown in the figure ).

As long as a certain voltage is applied to both ends of the coil, a certain current will flow through the coil to generate electromagnetic effects, and the armature will attract the iron core against the pulling force of the return spring under the action of electromagnetic force attraction, thereby driving the moving contact and the static contact (normally open contact) to attract. When the coil is disconnected, the electromagnetic suction will also disappear, and the armature will return to the original position under the reaction force of the spring, releasing the moving contact and the original static contact (normally closed contact). This pulls in and releases, thus achieving the purpose of turning on and off in the circuit. The "normally open and closed" contacts of the relay can be distinguished in this way: the static contacts on disconnected state when the relay coil is powered off are called "normally open contacts"; the static contacts on connected state are called "normally closed contact". The module comes with 2 positioning holes for you to fix the module to other equipment.

Specifications：

Working voltage: 5V (DC)
Interface: G, V, S interface
Input signal: digital signal (high level 1, low level 0)
Contacts: static contacts (normally open contacts, normally closed contacts) and moving contacts
Rated current: 10A (NO) 5A (NC)
Maximum switching voltage: 150 V (AC) 24 V (DC)
Electric shock current: less than 3A
Weight: 15g
Contact action time: 10ms

Equipment：

Connection Diagram：

Note: On the shield, the G, V, and S pins of 1-channel relay module are connected to G, V, and 12 respectively. The NO is linked with V; the G, V, and S pins of white LED are respectively connected to G, V, and the static contact of NO on relay module.

Test Code：

/*
Keyestudio smart home Kit for Arduino
Project 5
Relay
http://www.keyestudio.com
*/
int Relay = 12; // Define the relay pin at D12
void setup ()
{
pinMode (13, OUTPUT); // Set Pin13 as output
digitalWrite (13, HIGH); // Set Pin13 High
pinMode (Relay, OUTPUT); // Set Pin12 as output
}
void loop ()
{
digitalWrite (Relay, HIGH); // Turn off relay
delay (2000);
digitalWrite (Relay, LOW); // Turn on relay
delay (2000);
}
//

Test Result： Wire, power up and upload test code. The relay is connected(“NO” is on , NC is off) for 0.5s, then disconnected for 0.5s (NC is on, NO is off), and alternately. When the relay is connected, the white LED will be on, conversely, the white LED will go off.

Project 6：Photocell Sensor

Description

The photocell sensor (photoresistor) is a resistor made by the photoelectric effect of a semiconductor. It is very sensitive to ambient light, thus its resistance value vary with different light intensity. We use its features to design a circuit and generate a photoresistor sensor module. The signal end of the module is connected to the analog port of the microcontroller. When the light intensity increases, the resistance decreases, and the voltage of the analog port rises, that is, the analog value of the microcontroller also goes up. Otherwise, when the light intensity decreases, the resistance increases, and the voltage of the analog port declines. That is, the analog value of the microcontroller becomes smaller. Therefore, we can use the photoresistor sensor module to read the corresponding analog value and sense the light intensity in the environment. It is commonly applied to light measurement, control and conversion, light control circuit as well.

Specifications：

Working voltage: 3.3V-5V (DC)
Interface: 3PIN interface
Output signal: analog signal
Weight: 2.3g

Equipment:

Connection Diagram：

Note: On the expansion board, the G, V, and S pins of the photocell sensor module are connected to G, V, and A1; the G, V, and S pins of the yellow LED module are linked with G, V, and 5 separately.

Test Code：

/*
Keyestudio smart home Kit for Arduino
Project 6
photocell
http://www.keyestudio.com
*/
int LED = 5; // Set LED pin at D5
int val = 0; // Read the voltage value of the photodiode
void setup () {
       pinMode (LED, OUTPUT); // LED is output
       Serial.begin (9600); // The serial port baud rate is set to 9600
}
void loop () {
       val = analogRead (A1); // Read the voltage value of A1 Pin
       Serial.println (val); // Serial port to view the change of voltage value
       if (val <900)
       {// Less than 900, LED light is off
       digitalWrite (LED, LOW);
       } 
       else 
       {// Otherwise, the LED lights up
       digitalWrite (LED, HIGH);
       }
       delay (10); // Delay 10ms
} 
//

Test Result：

LED will be on after uploading test code, point at the photocell sensor with flashlight (or the flash from cellphone), you’ll find that LED is automatically off. However, take away the flashlight, LED will be on again.

Review For this code string, it is simply. We read value through analog port, please attention that analog quantity doesn’t need input and output mode.Read the analog value of photocell sensor by analog port.

The analog value will gradually decreases once there is light, the value is up to 1000, this value can be chosen according to brightness you need. Select method: put the whole device in the environment where LED is off, open serial monitor to check shown value, replace 1000 with this value. Read value from serial monitor is a good way to modulate code

Project 7：Adjusting Motor Servo Angle

Description

When we make this kit, we often control doors and windows with servos. In this course, we’ll introduce its principle and how to use servo motors. Servo motor is a position control rotary actuator. It mainly consists of housing, circuit board, core-less motor, gear and position sensor. Its working principle is that the servo receives the signal sent by MCU or receiver and produces a reference signal with a period of 20ms and width of 1.5ms, then compares the acquired DC bias voltage to the voltage of the potentiometer and outputs a voltage difference.

Servo motor comes with many specifications. But all of them have three connection wires, distinguished by brown, red, orange colors (different brand may have different color). Brown one is for GND, red one for power positive, orange one for signal line.

The rotation angle of servo motor is controlled by regulating the duty cycle of PWM (Pulse-Width Modulation) signal. The standard cycle of PWM signal is 20ms (50Hz). Theoretically, the width is distributed between 1ms-2ms, but in fact, it's between 0.5ms-2.5ms. The width corresponds the rotation angle from 0° to 180°. But note that for different brand motor, the same signal may have different rotation angle.

There are two ways to control a servomotor with Arduino. One is to use a common digital sensor port of Arduino to produce square wave with different duty cycle to simulate PWM signal and use that signal to control the positioning of the motor. Another way is to directly use the Servo function of the Arduino to control the motor. In this way, the program will be easier but it can only control two-contact motor because for the servo function, only digital pin 9 and 10 can be used. The Arduino drive capacity is limited. So if you need to control more than one motor, you will need external power.

Specifications:

Working voltage: DC 4.8V ~ 6V Operating angle range: about 180 ° (at 500 → 2500 μsec) Pulse width range: 500 → 2500 μsec No-load speed: 0.12 ± 0.01 sec / 60 (DC 4.8V